Searching For A Source

There is a very beautiful song [sang at the siyum hashas] that goes כד יתבין ישראל ועסקין בשמחת התורה, קודשא בריך הוא אומר לפמליא דיליה חזו בני חביבי דמשכחין לצערא דילהון ועסקין בחדוותא דילי - When the Jews sit and are involved in the simcha of Torah Hakadosh Baruch Hu says to His holy group of angels  - Look at my beloved children who forget about there own pain and are involved in my joy.

It is so touching and I really want to believe Hashem says it. The problem is that I have been looking for the source for a long time and just because it is so moving [especially when put to music or when it was quoted at the funeral of a young yeshiva boy who was murdered], that doesn't mean it's true.

According to Wikipedia [SHLITA!] the closest thing we can find is a comment of Rebbe Avraham ben HaGra in his sefer Ba'er Avraham [Vilna 1887]: ראו בנים חביבים שיש לי דשבקין צערא דידהו ועסקין
בדידי, מיד מתמלא רחמין על ישראל
See my beloved children who leave there own pain and involve themselves in my [Torah], immediately He is filled with mercy for the Jewish People.

Close....

Even if we have no earlier source - it makes sense that Hashem has tremendous nachas ruach when we forget our own pain and immerse our entire being into His Torah.

Also -  if we believe it, that may cause it to happen. The power of Emunah is NOT to be underestimated....  

Any insight sweet friends?